Pseudo-code. I can post the full code if it helps.
On Feb 14, 2011, at 3:35 PM, Sven-Thorsten Dietrich <thebigcorporation@xxxxxxxxx> wrote:
> On Mon, 2011-02-14 at 15:08 -0800, Peter LaDow wrote:
>> Note sure how that is possible. This is related to my earlier posting
>> about timing jitter. Our code is basically this:
>>
>
> Where is the semicolon ending the for loop?
>
>
>> while(1)
>> {
>> t1 = clock_gettime()
>> for(i=0; i < 10000; i++)
>> t2 = clock_gettime()
>>
>> diff = t2 - 1
>> }
>>
>> This task is pending on nothing. Unless clock_gettime() causes some
>> sort of priority inversion, I don't see the problem. We see
>> significant jitter on the for-loop when there are a significant number
>> of other kernel timers. Now, as we understand it, the hrtimers run in
>> the softirq. But if the softirq is priority 50, and this for-loop is
>> priority 99, it shouldn't be affected by the softirq thread.
>>
>> Pete
>>
>> On Mon, Feb 14, 2011 at 3:04 PM, Sven-Thorsten Dietrich
>> <thebigcorporation@xxxxxxxxx> wrote:
>>> On Mon, 2011-02-14 at 14:31 -0800, Peter LaDow wrote:
>>>> How is the scheduling of the hrtimers softirq thread handled?
>>>>
>>>> When querying the RT priority of the hrtimer softirq, I get a priority
>>>> of 50. But when running a priority 99 thread, we still seem to be
>>>> getting interrupted. Shouldn't the hrtimer softirq be put off until
>>>> the CPU is idle or a lower priority task is running?
>>>
>>> Does your prio 99 thread perhaps encounter a prio inversion dependency
>>> on one of the softriq threads?
>>>
>>>>
>>>> Thanks,
>>>> Pete
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>>>
>>>
>>>
>
>
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